Medication delivery pens are hypodermic syringes used for self-injection of precisely measured doses of medication. Pens are widely used, for example, by diabetics to dispense insulin.
A typical prior art medication delivery pen includes a cartridge which contains a volume of liquid medication sufficient for several doses. The dose is injected into a tissue area, such as the intramuscular tissue layer, the subcutaneous tissue layer, or the intradermal tissue layer.
The assembly and operation of a typical pen injection device, as shown in FIGS. 1 and 2, is described in U.S. Patent Application Publication No. 2006/0229562, published on Oct. 12, 2006, which is hereby incorporated by reference in its entirety.
Pen injection devices, such as the exemplary pen injector 100, as shown in FIGS. 1 and 2, typically comprise a dose knob/button 24, an outer sleeve 13, and a cap 21. The dose knob/button 24 allows a user to set the dosage of medication to be injected. The outer sleeve 13 is gripped by the user when injecting medication. The cap 21 is used by the user to securely hold the pen injector device 100 in a shirt pocket, purse or other suitable location.
FIG. 2 is an exploded view of an exemplary drug delivery pen shown in FIG. 1. The dose knob/button 24 has a dual purpose and is used to both set the dosage of the medication to be injected and to inject the dosed medicament via the lead screw 7 and stopper 15 through the medicament cartridge 12, which is attached to the drug delivery pen through a lower housing 17. In standard drug delivery pens, the dosing and delivery mechanisms are all found within the outer sleeve 13 and are not described in greater detail here as they are understood by those knowledgeable of the prior art. The distal movement of the plunger or stopper 15 within the medicament cartridge 12 causes medication to be forced into the needle 11 of the hub 20. The medicament cartridge 12 is sealed by septum 16, which is punctured by a septum penetrating needle cannula 18 located within the hub 20. The hub 20 is preferably screwed onto the lower housing 17, although other attachment means can be used such as attaching to the cartridge. To protect a user, or anyone who handles the pen injection device 100, an outer shield 69, which attaches to the hub 20, covers the hub. An inner shield 59 covers the patient needle 11 within the outer shield 69. The inner shield 59 can be secured to the hub 20 to cover the patient needle 11 by any suitable means, such as an interference fit or a snap fit. The outer shield 69 and inner shield 59 are removed prior to use. The cap 21 fits snugly against outer sleeve 13 to allow a user to securely carry the drug delivery pen 100.
The medicament cartridge 12 is typically a glass tube sealed at one end with the septum 16 and sealed at the other end with the stopper 15. The septum 16 is pierceable by a septum penetrating cannula 18, but does not move with respect to the medicament cartridge 12. The stopper 15 is axially displaceable within the medicament cartridge 12 while maintaining a fluid tight seal.
The outer shield 69 and the inner shield 59 are removed from the hub 20 and needle 11 prior to injecting a patient with the medicament stored in the cartridge 12. Some patients become uncomfortable at the sight of the needle 11, which is visible prior to the injection. Accordingly, a need exists for a pen injection device having a hub assembly that prevents a patient from seeing the needle prior to an injection.